Good question - so, border crossings in general:
Depending on the circumstances, border-crossing posts range from "soft" structures that do little more than protect the border personnel from inclement weather, to hardened and revetted bunkers that look tough enough to shrug off a tactical nuke. Two buildings guard most crossings: one handles traffic bound into the sector, while the other handles outbound traffic. Depending on the strecth of the Boundary in question, these two establishments often belong to two different nations - who sometimes despise each other.
Security at border-crossing posts varies too. From a skeleton crew of three or four lightly armed officers to a dozen heavily armed "customs officials" supported by a fire team of skullcrushers and at least one combat mage for astral backup. Vehicular support ranges from none to an APC or two.
The standard level of security along a demarcation line is a double fence line, reinforced, 10 meteres high, alarmed, and sometimes electrified.
At least 20 meters of no man's land separate the two lines of the fence and sometimes more. A low single wire fence running down the center of the no man's land marks the official border but it is purely symbolic, bcause anyone older than about three can step over it easily. You can install whatever security provisions you like on your side of the no man's land - patrols, land mines, whatever.
There are two types of border crossings: Walkovers and Vehicular crossing points:
If you want to walk through, then take the kind of security checkpoint you go through at an airport and jack up the intensity a couple of notches. That will give you a pretty good idea of the typical pedestrian crossing point. Everyone going through the crossing point must walk through an archway just jam packed with sensors - metal detectors, MADs, chem sniffers, just to get into the "processing area' Anyone who triggesr the sensor array will attract the attention of a handful of very large, very mean gentlemen and ladies, typically wearing full armor and packing submachineguns.
Once you are through the scanner arch, the fun is only beginning. You'll have to explain to some immigration official why you want to enter the sector, how long you will be there, where you will be staying, etc. As you are doing this, you will be asked to provide your SIN for inspection.
There are "Frequent Traveler" passes which you can acquire, but you must apply in person to the immigration agencies of both sectors, convince them that you are no security threat and that you truly warrant "Frequent Traveler" status. If you can do this, you receive a passcard with a microtransponder, which will not be replaced, and contains information coded to the SIN you used to acquire it. If you lose it, it will not be replaced.
If you are a Frequent Traveler, you pass through the arch, but then instead of talking to immigration, you pass through another doorway, where the system interrogates the passcard and compares it to existing records. As long as it matches, you just walk through. If not, then expect to see the inside of one of those little interrogation rooms.
If you are crossing by vehicle, then it is much more of a production than passing through by walking. Generally, everybody in a vehicle has to get out and submit to the same kind of checkpoint process as a traveler at a pedestrian crossing. At the guard's request, all luggage and objects in the car must be unloaded for a hand inspection. Meanwhile the car, or whatever the vehicle happens to be, gets its own going-over. The level of attention, shall we say, varies depending on a wide range of factors - whether the driver and passenger look harmless or suspicious, whether hter is any reason to suspect something amiss, the level of suspicion between the sectors, etc. One day, the border grunts give your car a quick once-over with a hand held chm sniffer and scopes out the underside with mirrors, taking a grand total of sixty seconds. The next day they fragging near strip it down to the frame.
Specific to the CAS, you know that:
The CAS Sector lines its borders with 10 meter high fences, interrupted in a few spots by walls. Along the stretch between the CAS and UCAS sectors that swings roughly south between Denver and Colorado Springs and passes through Elbert and Peyton, the fence drops to 5 meters high.
In most of the places they patrol, CAS Sector security forces take a hands on approach, walking their side of the line in three-man fire teams, often accompanied by attack dogs.
Unlike other sectors, CAS protects its borders with sophisticated sensor arrays only in a few highly sensitive areas, usually concentrated along the rural stretches of the sector border.
To answer your specific question, no. While there is not a mage at every border crossing, there are Watchers and other Spirits set up to spot those trying that exact trick.